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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: SMURF amplifier block list
Anyone mind sharing that conversation? On Wed, 15 Apr 1998, James R. Cutler wrote: :Jay, : :I now understand the confusion -- You are speaking of the :dotted decimal representation of the 32 bit IP address without :regard to masking. I am speaking of the masked address which :results in a (mask length) network number part and a :(32 - mask length) host number. This means you think of :address components as octets (bytes) and I think of the :effective network number and the effective host number, the :sizes of which are determined only by the mask. : :Or another way to this is that the routers and hosts do not :see the dotted notation except in the configuration dialogs. :Internal to the routing processes the effective network :number determines the routing between subnets and a broadcast :address is any address where the host number is all ones. : :Another way to look at this is to say you are thinking about :IP addressing in a "classful" manner whilst I am speaking in :a "classless" manner. Believe me, the transition from classful :to classless thinking in IP addressing is not an easy thing. :None of the RFCs are simple to understand. : :So, I guess I'm not in trouble after all. : :Regards. : : JimC : : :At 8:49 PM -0400 4/14/98, Jay R. Ashworth wrote: :>On Tue, Apr 14, 1998 at 04:52:06PM -0400, James R. Cutler wrote: :>> I have a B assignment. I have switched infrastructure segments :>> with /22 masking. Do you mean to say that the host number :>> range on each /22 masked segment is not continuous 1 through 1022, :>> but has several holes instead.? The network seems to be working :>> properly. I may be in big trouble! :>> :>> None of my TCP/IP courses or books or Cisco CDs have prepared me for :>> such a surprise. Please point me to a text which will explain this. :> :>None of my study of TCP in the past 5 years has prepared me for the :>idea that someone might think that any component of an IP address might :>be greater than 255. They're decimal representations of _8 bit_ :>numbers. :> :>No matter _where_ the net/subnet break is, you _still_ _write_ them as :>AAA.BBB.CCC.DDD. :> :>Yes, conceptually, you might _read_ the addresses that way, but I'm :>pretty sure that not one piece of equipment you own will let you :>_write_ them that way, will they? :> :>Now, to get back to the conversation at hand: the proposition was that :>blocking ingress to addresses ending in .255 makes it much more :>difficult for your network to be used as a "smurf amplifier" (and if :>you don't know what that is, you haven't been following the discussin :>(and links) on this list in the last month or 3). :> :>Yes, if you have internal networks larger than a /24, then that means :>you'll lose extra addresses if you do this. :> :>The point is that if you _don't_ avoid using host addresses that end in :>.255 _whether that address is a broadcast address based on your netmask :>or not_, then you're likely to find yourself with hosts that either can't :>talk, or can't be talked _to_. :> :>Now have I made myself clear? :> :>Cheers, :>-- jra :>-- :>Jay R. Ashworth [email protected] :>Member of the Technical Staff Unsolicited Commercial Emailers Sued :>The Suncoast Freenet "Two words: Darth Doogie." -- Jason Colby, :>Tampa Bay, Florida on alt.fan.heinlein +1 813 790 7592 :> :>Managing Editor, Top Of The Key sports e-zine ------------ http://www.totk.com : :- :James R. Cutler :EDS , 800 Tower Drive, Troy, MI 48098 :Phone: +1 248 265 7514 FAX: +1 248 265 7514 :EDS Internal Web: <http://www.iscg.eds.com/cutler/> :World Wide Web: <http://www.ltu.edu/midecus/dechtm/cutler/cutler.htm> : -- Regards, Jason A. Lixfeld [email protected] iDirect Network Operations [email protected] --------------------------------------------------------------------- TUCOWS Interactive Ltd. o/a | "A Different Kind of Internet Company" Internet Direct Canada Inc. | "FREE BANDWIDTH for Toronto Area IAPs" 5415 Dundas Street West | http://www.torontointernetxchange.net Suite 301, Toronto Ontario | (416) 236-5806 (T) M9B-1B5 CANADA | (416) 236-5804 (F) ---------------------------------------------------------------------
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